Many scientists contend that release of refrigerants into the atmosphere deleteriously affects the ozone layer that surrounds and protects the earth from ultraviolet solar radiation. Recent international discussions and treaties, coupled with related regulations and legislation, have renewed interest in devices for recovery and storage of used refrigerants from refrigeration equipment for later purification and reuse or for proper disposal. U.S. Pat. No. 4,261,178, assigned to the assignee hereof, discloses a refrigerant recovery system in which the inlet of a compressor is coupled through an evaporator and through a manual valve to the refrigeration equipment from which refrigerant is to be recovered. The compressor outlet is connected through a condenser to a refrigerant storage container. The condenser and evaporator are combined in a single assembly through which cooling air is circulated by a fan. Content of the storage container is monitored by a scale upon which the container is mounted for sensing weight of liquid refrigerant in the container, and by a pressure switch coupled to a the fluid conduit between the condenser and the container for sensing vapor pressure within the storage container. A full-container condition sensed at the scale or a high-pressure condition sensed at the pressure switch terminates operation of the compressor motor. A vacuum switch is positioned between the inlet valve and the evaporator for sensing evacuation of refrigerant from the refrigeration equipment and automatically terminating operation of the compressor motor.
U.S. Pat. No. 4,768,347, also signed to the assignee hereof, discloses a refrigerant recovery system that includes a compressor having an inlet coupled through an evaporator and through a solenoid valve to the refrigeration equipment from which refrigerant is to be withdrawn, and an outlet coupled through a condenser to a refrigerant storage container or tank. The refrigerant storage container is carried by a scale having a limit switch coupled to control electronics to prevent or terminate further refrigerant recovery when the container is full. The scale comprises a platform pivotally mounted by a hinge pin to a wheeled cart, which also carries the evaporator/condenser unit, compressor, control electronics, and associated valve and hoses.
Although the systems disclosed in the noted patents address and overcome problems theretofore extant in the art, further improvements remain desirable. For example, a problem remains relative to recovering refrigerant from large commercial chiller systems and the like that employ low-pressure refrigerants such as R11 and R123. The boiling point of trichloro-monofluoromethane (R11) is 74.9.degree. F., and the boiling point of dichloro-trifluoroethane (R123) is 82.2.degree. F. In order to function at normal evaporation temperatures in the 40.degree. to 50.degree. F. range, each of these refrigerants must operate at a considerable vacuum. A recovery system for low-pressure refrigerant of this character would require an significant amount of auxiliary heat in an evaporator if the refrigerant were pumped during recovery only in vapor phase, requiring accessive energy and long recovery times.
It is therefore a general object of the present invention to provide a system for recovering low-pressure refrigerants in which the refrigerant is recovered primarily in liquid phase, in which recovery time is optimized as a function of input refrigerant phase, and/or in which heating of inlet refrigerant is minimized. Another and more specific object of the present invention is to provided a refrigerant recovery system of the described character in which a compressor is employed for drawing refrigerant from equipment under service, and in which a liquid refrigerant pump is employed to bypass liquid refrigerant from the compressor directly to a refrigerant storage container. Another and related object of the present invention is to provide a refrigerant recovery system of the described character that operates automatically without operator intervention.